For years people have been attempting to develop a convenient screening assay to determine whether a patient has Primary Open Angle Glaucoma (POAG) or is at risk for developing POAG. The currently used diagnosis is based on an evaluation of a patient's visual field and many risk factors such as intraocular pressure, family history of Glaucoma, race, age, and the appearance of the optic disk. All of these factors are considered in reaching the diagnosis of POAG. However, the testing is not simple, requires a highly skilled person for proper evaluation, and is extremely time-consuming and expensive and is unreliable.
Because of the above-referenced current method of diagnosis of POAG or risk for developing POAG, there is a continuing need and has been a continuing search for a clear marker, or test system, that can be used in mass testing of the public to determine POAG risk. In earlier work of these co-inventors reported in U.S. Pat. No. 4,863,912, and a divisional application which matured into U.S. Pat. No. 4,997,826, these present co-inventors developed a therapy for Tetrahydrocortisol use in Glaucoma treatment.
Tetrahydrocortisol is a normal cortisol metabolite found in urine and serum of normal humans but not in Trabecular Meshwork (TM) cells isolated from POAG eyes. Cortisol is metabolized only slowly by normal TM cells. However, in TM cells from primary open angle glaucoma (POAG) patients, the rate limiting enzyme delta-4-reductase is aberrantly hyperexpressed, and activity of the 3-oxidoreductase (also called 3-hydroxysteroid dehydrogenase) is reduced. This enzyme imbalance leads to the accumulation of 5-alpha and 5-beta-dihydrocortisol in POAG TM cells. It was in these patients that it was postulated that 5-beta-dihydrocortisol is toxic to TM cells and compromises TM function. Since the trabecular meshwork is the major site for aqueous humor outflow, compromised TM function leads to an increase in intraocular pressure. It is believed that tetrahydrocortisol may antagonize the action of 5-beta-dihydrocortisol, in a yet to be defined manner, and that it also may function as an inhibitor of A-ring reductase activity.
In earlier work of these co-inventors reported in 1983 in Investigative Ophthalmology & Vis Science (24:1413, 1983) and 1985 in Investigative Ophthalmology and Vis Science (26:890, 1985), it was reported that 5-beta-dihydrocortisol is metabolized in the TM cells by an enzyme 3-alpha-hydroxysteroid dehydrogenase (3-alpha-HSD) to 3-alpha, 5-Beta-Tetrahydrocortisol. This is a normal metabolic pathway. In the earlier work as reported, the inventors identified two enzyme defects in cultured trabecular meshwork from patients with Primary Open Angle Glaucoma. As compared to control cells, the POAG derived cells had an increase in cortisol delta 4-reductase and a decrease in 3-alpha-hydroxysteroid dehydrogenase. This finding, however, had little diagnostic value since it required culturing cells from either autopsy eyes or from surgical specimens. Put another way, an assay on cells from the TM is simply not practical as something that can be used on the population at large to determine POAG risk. Therefore, in 1983 in an effort to find a further diagnostic assay, an enzyme which was observed to have a dramatic increase in patients suffering from trabecular meshwork cells, namely cortisol delta-4 reductase, was tested in peripheral lymphocytes from blood samples of patients known to be suffering from Glaucoma as compared to patients known not to be suffering from Glaucoma. The levels of cortisol delta-4 reductase were found to be the same in POAG and non-POAG derived specimens. Therefore, it was then concluded that there was no correlation between levels of this enzyme in the TM and the levels in cells in the blood specimens, and the search for a correlating enzyme as a diagnostic marker stopped.
It can be seen that there is a real and continuing need for a simple, general population test that can be used on the public at large by laboratory workers to determine patient risk of Primary Open Angle Glaucoma.
Thus it is a primary objective of the present invention to provide a mass screening assay which can be used as a marker test for POAG and those patients at risk of developing POAG, which are collectively referred to herein as "at risk" patients.
Another objective of the present invention is to provide such an assay which is simple, straightforward and which can be properly interpreted by people of lower skill levels than those required to make the overall composite evaluations presently used in the medical field that involve such subjective data as evaluation of visual field, family history, race, age and appearance of the optic disk.
Another objective of the present invention is to develop a simple blood assay test which correlates predictably and easily and quickly with Primary Open Angle Glaucoma risk determination.
Yet another objective of the present invention is to develop a simple testing kit which can be used in determining Primary Open Angle Glaucoma risk.
The method and means of accomplishing these objectives as well as others will become apparent from the detailed description of the invention which will follow hereinafter.